FIG. 8 shows one type of a chain structure.
A chain 160 is provided with platy pin link plates (outer link plates) 162 opposed to each other, and a pin insertion hole is made in each of both ends of the pin link plate (the outer link plate) 162.
Further, the chain 160 is provided with platy bush link plates (inner link plates) 164 opposed to each other, and a bush fitting hole is made in each of both ends of the bush link plate (the inner link plate) 164.
Each of fitting portions on both ends of a cylindrical bush 166 is fitted into the bush fitting hole, and a cylindrical roller 168 is fitted rotatably on an outer circumference of the bush 166.
Both the ends of the bush 166 are each provided with the fitting portion fitted into each of the bush fitting holes of the bush link plates (the inner link plates) 164, and a central portion of the bush 166 is provided with a pin through hole penetrated by a pin 170.
Further, the chain 160 is provided with rod-like pins 170. A cylindrical main body of the pin 170 is allowed to penetrate the pin through hole of the bush 166, and each end of the pin 170 is locked to the pin link plate (the outer link plate) 162.
The chain 160 is thus assembled and thereby is structured by flexibly linking these parts.